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From "Philip Zeyliger (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-245) Create symbolic links in HDFS
Date Thu, 17 Sep 2009 21:27:57 GMT

    [ https://issues.apache.org/jira/browse/HDFS-245?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12756799#action_12756799
] 

Philip Zeyliger commented on HDFS-245:
--------------------------------------

In my opinion (I'd say IME, but I've never sneaked one of these past code review),using exceptions
for flow control is shady.  Joshua Bloch would say the same ("Don't force client to use exceptions
for control flow" see page 38, http://74.125.155.132/search?q=cache:MmIXuflmcvcJ:lcsd05.cs.tamu.edu/slides/keynote.pdf+joshua+bloch+exceptions&cd=4&hl=en&ct=clnk&gl=us&client=firefox-a
or http://lcsd05.cs.tamu.edu/slides/keynote.pdf ).

If the worry is about boilerplate, it seems like this exception
would have to be checked --- otherwise, people would not know that
this exception is part of what they have to handle and implement ---
and nothing introduces misunderstood boilerplate quite as fast as
checked exceptions.

I can't think of many analogous interfaces here; the lack
of which probably makes this argument more contentious.
HTTP is vaguely similar: there's sometimes a full response,
and sometimes there's a redirection.  In most APIs wrapping
HTTP that I've seen, you get a response object in response
to a request.  TCP/IP errors (socket timeouts, name resolution, etc.)
throw exceptions, but nothing that has to do with HTTP does.  
One inspects response.status to see if it's 200 (ok), 301 (redirect), etc.

-- Philip

> Create symbolic links in HDFS
> -----------------------------
>
>                 Key: HDFS-245
>                 URL: https://issues.apache.org/jira/browse/HDFS-245
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>            Reporter: dhruba borthakur
>            Assignee: Eli Collins
>         Attachments: 4044_20081030spi.java, HADOOP-4044-strawman.patch, symlink-0.20.0.patch,
symLink1.patch, symLink1.patch, symLink11.patch, symLink12.patch, symLink13.patch, symLink14.patch,
symLink15.txt, symLink15.txt, symLink4.patch, symLink5.patch, symLink6.patch, symLink8.patch,
symLink9.patch
>
>
> HDFS should support symbolic links. A symbolic link is a special type of file that contains
a reference to another file or directory in the form of an absolute or relative path and that
affects pathname resolution. Programs which read or write to files named by a symbolic link
will behave as if operating directly on the target file. However, archiving utilities can
handle symbolic links specially and manipulate them directly.

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